Mechanics

ENGINE COOLANT TEMPERATURE SENSORS

1995 Mercedes Benz SL600 • V12 2WD Automatic • 72,000 miles

The 1995 SL600 V-12 mercedes has 2 coolant temperature sensors with 4 pins that are not numbered. The new wiring harness has 2 plugs with 4 receptacles that are numbered 1 through 4. How do I know I am attaching the plug properly? There is no groove or deviation to ensure one way attachment of the plug.
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Copycar
March 3, 2011.



Are you replacing ECTs? Or a wiring harhess? Is this a BOSCH part or after market?

Docfixit
Mar 3, 2011.
I replaced the engine wiring harness with Mercedes dealer purchased harness and noticed that the new harness has the 2 numbered plug receptacles. The CTS in the engine are the original bosch products and the 4 pins are not numbered.

Tiny
Copycar
Mar 3, 2011.
Mercedes does not provide complete wiring diagrams so have no way to trace wiring. Have you contacted dealer as to problem if harness was changed they would have directions or TSB. Can you match up old wiring colors to new and does color change at pigtail to ECT?

Docfixit
Mar 3, 2011.
The new harness matches perfectly. The old harness plugs have the same numbered receptacles and I carefully marked the position of the old plugs with crayon before removal. I could make a determination of the pin position based on this marking but would rather have a definite answer.

Tiny
Copycar
Mar 3, 2011.
You will have to get that from dealer

Docfixit
Mar 3, 2011.
The mechanic at the dealer claims he does not know. I would think if it mattered that there would be a groove or deviation in the CTS that would allow only one way of connecting the plug. Perhaps it does not matter?

Tiny
Copycar
Mar 3, 2011.
I would go with pin position it will not harm if it is wrong. May get a engine light

Docfixit
Mar 3, 2011.
I will try that and if it runs rough while cold I can shut down and reposition each plug clockwise one pin until it smooths out.

Tiny
Copycar
Mar 3, 2011.
Great idea let me know what happens

Docfixit
Mar 4, 2011.
I discovered that the pins diagonally from each other complete the circuit and operate the same valves. Therefore it does not matter which way the plug is attached.

I completed the installation of the engine wiring harness and now the engine will not start.
Do I have to clear the computer before it will start?
The car was running when I drove it into the shop to replace the engine wiring harness. The old harness was completely falling apart with some of the wiring completely bare of insulation and the engine still ran.

Tiny
Copycar
Mar 7, 2011.
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